|Sundevall , 1833|
The harvestmen (Opiliones), also called Kanker, Schneider, Schneidergeiß, Schuster, Waldschreit, Zimmermann and Grandpa Langbein , are an order of the arachnids (Arachnida). About 6600 species with body lengths of 2 to 22 millimeters are known worldwide. The harvestmen contain species that are compact and mite-shaped, but also the well-known long-legged species. The largest representatives of the harvestmen are Trogulus torosus (family: Trogulidae) with a body length of 22 millimeters and Mitobates stygnoides with a body length of only 6 millimeters, but with legs 160 millimeters long. In Central Europe, several species of harvestmen are at least regionally endangered.
The most important distinguishing feature to the weaving spiders is a so-called intergrowth of the front ( prosoma , cephalothorax ) and rear body ( opisthosoma ); the opisthosoma is always structured. Harvestmen have neither spinneret glands nor poison glands in the narrower sense, but stink glands , which usually secrete toxic substances. In contrast to spiders, they have a real sex organ with a penis .
Harvesters belong to the group of arachnids ; in them the prosoma is attached to the opisthosoma over the full width . This creates a compressed egg-shaped to rounded shape. The individual segment rings - probably 16 embryonically created - have been partially lost (reduced) or merged into one another. The distinction between sternites (sclerotized chest part of a segment) and tergites (the same on the back) is only recognizable in embryos. Your first pair of extremities are the three-part chela (mouthparts, chelicerae ), the second pair of extremities, pedipalpus , is designed as a (leg-like) tactile or grasping organ. Pairs of extremities III to VI are pairs of legs I to IV. Breathing openings are spiracles on the second sternite of the opisthosoma. The semen is transmitted through a penis. In addition, the anal opening ( operculum anale ), openings of the stinking glands, the group of thorns and the ocular hillock belong to the rough overview of the body structure . There can also be sexual dimorphism in harvestmen. Males of the Laniatores are noticeably darker than the females because their chitin cover is thicker. In addition, they usually have a much stronger sculpting.
The back shield ( dorsal scutum ) of the cephalothorax consists of the first five to six tergites that are more or less fused together. The tergites of the dorsal abdomen are rarely fused, more often they are isolated and clearly separated from each other. The structure of the back is an important determinant. One distinguishes
- Scutum completum: abdominal plate of the abdomen (segments I to VIII) and dorsal shields of the anterior and posterior abdomen completely fused together, found in Sironidae and Oncopodidae .
- Sc. magnum: abdominal plate consists of segments I to V, remaining segments isolated, prosomal plate completely fused, both scuti fused. Characteristic of most of the Laniatores, Palpatores, Trogulidae, Nemastomatidae.
- Sc. parvum: last abdominal tergite separated, scutum separated from the front and rear body and freely movable, last two or three tergites of the abdomen isolated, e.g. B. Phalangioidea.
- Sc. tenue: similar to parvum, but with thin sclerite plates, found in Phalangiidae, Gagrelinae.
- Other forms are Sc. laminatum, Sc. intermedium, Sc. dissectum or Sc. called compositum .
The scutum is usually fully developed during adult moult , only the Sc. compositum only after adult moult.
For species that live in the litter layer ( epigeic ), the pattern of the drawing is always species and sex-specific. For species in the herb layer, z. B. Nemastomatidae, the pattern is variable within a species within narrow limits. However, the body coloration varies greatly among all harvestmen. On the one hand, it is subject to a considerable individual expression and changes in the course of life even after adult moult, with hardening of the exoskeleton . The color also varies depending on the habitat (biotope), altitude or stratum. In Mitopus morio ( Phalangiidae ), variations in pattern and color depending on the altitude of the biotope were detected.
Integument with micro and macro sculptures
The body of some species is covered with sometimes bizarre and colorful thorns and prongs that can only be seen under the microscope. The function of these body processes is still unclear. They are formed from the integument and structure scuta and sclerite much more strongly than with all other arachnids. They can appear as relief-like structures, cusps, bridge thorns (Nemastomatidae), bulges, cones, thorns, tubercles , on the scutum or on the pedipalps (Laniatores), or on the chelicerae ( Ischyropsalis ). These structures in turn often have smaller hairs or tubercles. The microsculpture of the skin (cuticle) includes relief formations, innervated sensory hair, massive microtrichia (fake hair), dentition, granulation and stridulation organs . In contrast to the weaving spiders, the hairiness plays a subordinate role and trichobothria are missing. A particular specialization, however, is glandular hair and feather hair (pedipalps) as well as granule fields (granules). Microtrichia are mainly found on the pedipals and treadmills and are mostly located distally. All hair is used for sensory perception, mainly sensory.
Other sensory organs are the sensilla or cleft sense organs , which correspond to the lyre-shaped organs in real spiders . In contrast to the lyre-shaped organs of the weaving spider, which consist of an accumulation of sensory fissures, these are only found individually and in significantly smaller numbers in harvestmen (up to 3000 in Cupiennius salei , in some harvestmen approx. 45). More precise knowledge about the function of the cleft sense organs in harvestmen is not yet available, however, as with the weaving spiders, these should serve for orientation, perception of one's own body movement and perception of airborne sound.
Some species, within the Trogulidae, Dicranolasmatidae and Selerosomatinae, have a glandular-papillary skin with which secretions are excreted, to which soil parts adhere and thus form an earth mimicry. In Selerosomatinae, the secretion hardens to a porous, glassy coating. In Gagrellinae, the skin secretions are also colored and in some of them are grouped together to form larger glandular organs.
Like all arachnids, they have eight legs that are extremely long in many species. In Mitobates stygnoides , the legs can be 25 times the length of the body. There are also many species without this noticeable leg length or those with very short legs, which in some species are barely longer than the body. The first leg link, the hip (coxa) of the extremities, often has a lobe-shaped appendix called the maxillary lobe; these appendages can sometimes cover almost the entire underside of the prosoma. The lobi maxillares of the coxes of the second pair of extremities (the pedipalps) have diagnostic value in determining families.
- Walking legs
The four pairs of legs of the harvestmen are divided into coxa (hip), thigh ring (trochanter), femur (thigh), tibia (splint), metatarsus , tarsus and the claw organ (tarsal claw). The metatarsus and tarsus can consist of only one member or are secondarily divided in many ways; z. B. Phalangiidae (Leiobuninae) have over 100 individual members in the metatarsus and tarsus. These sham joints are not fully mobile and only consist of a very thin and flexible cuticle. The joint between the metatarsus and tarsus is heavily sclerotized and therefore easy to distinguish.
Such multiple articulated tarsi are unique among arthropods. They can be looped around blades of grass, leaves or twigs like a lasso, making them ideal for moving in the vegetation of the herbaceous and shrub layers. At the same time, they can be put on like a foot and act like an anchor when support on the ground is required.
The tarsal claws, with which the leg closes off like the real spider, are characteristic of larger groups. The claws of pairs of legs I and II are more simply constructed than the claws of pairs of legs III and IV. The structure of the claws and their ontogenetic development have not yet been conclusively clarified.
There are also glands on the walking legs, which are presumably secondary genital organs. Phalangodids also have tarsal glands for the same purpose.
Many species of Phalangiidae can autotome legs that are held on . Species with shorter legs cannot.
The pedipalps of many species often look like legs, so that the inexperienced observer can count five pairs of legs. They can (in the case of the Laniatores) be designed as catching organs that can be hammered in, but mostly serve for touch, reproduction or (in the case of food intake) as limbs that push food to the jaw claws ( chelicerae ).
Harvesters' pedipalps are divided into coxa, trochanter, femur, tibia and tarsus, similar to their treads, with the metatarsus missing and the tarsus always one-part. A tarsal claw is often missing. They serve as a tactile organ for the close range when catching prey (in the far range this is done by the walking legs), when eating or as a climbing aid ( Phalangiidae ). When the pedipalp is used as a tactile organ, it is covered with hairs of the senses ( Ischyropsalididae ), which are also partially specialized in glandular hairs ( troguloidea ). Laniatores in particular use the pedipalpus as a catch leg to strike prey and to hold on to it. With them, the sensory hairs on the palps are reduced to a minimum.
The chelicerae (jaw claws) arise below the edge of the cephalothorax and are connected to soft-skinned membranes. Some of these skins are sclerotized and covered with thorns. The jaw claws are tripartite. The third link is the chela . In some groups, regardless of their family affiliation, the base member is excessively elongated and body-length or longer (e.g. Ischyropsalididae ). The chelicerae carry secondary sexual characteristics such as glands or pores for secretion to escape, which play a role in courtship (e.g. Troguloidea ). These glands are mostly located in the basal phalanx, in some groups also in the anterior body; in other groups the chelicerae are completely permeated by secretion canals and have pores everywhere. Some genera have only one large gland in the front body, which conveys secretion to the chelicerae to the outside through a single collecting duct with a single outlet. The chelicerae are usually toothed in one row, the teeth being sclerotized and compact. In some groups, on the other hand, there is an additional double row of teeth on the outer cutting edge with teeth, which in turn have a saw-blade-like surface on the side.
A striking feature of all harvestmen under the microscope is a pronounced mound that bears the eyes. This eye mound can also be designed into a relatively long stem. The sense of sight is relatively poorly developed, even when ultraviolet light is perceived. What role this plays in these nocturnal animals is unclear.
All harvestmen have stink glands. Most of their outlets are on the front edge of the back; with the palpatores at the level of the first or second pair of legs, with the laniatores only at the level of the second coxa, with the cyphophtalmi at the level between the second or third hip on a dorso-lateral cone. In Trogulidae, Nemastomaditae and Ischyropsalidae, the openings on the lateral edge of the ophistosm and from above cannot be seen.
The secretion is a defensive secretion that escapes when the body is subjected to greater pressure or when attacked by insects or spiders. It is volatile or liquid, usually has a strong smell, but above all, depending on the concentration, can be numbing to fatal. If you lock Phalangiidae in a vessel, they numb themselves with their own secretion. Sironidae dab it with their walking legs and try to wet attackers with it. For others, it is a highly effective antibiotic that is believed to have a protective bacteriostatic influence on the animal's skin. Unused secretion flows backwards in channels and is distributed laterally to the coxa or outer skin.
Way of life of the harvestmen
The harvestmen, who mostly live in the soil layer, do not build fishing nets, but instead feed mainly on microscopic arthropods and also on dead insects. In the loose litter of the deciduous forest, in gardens, meadows, hedges or near-natural parks, they graze with their chelicerae from dead plant parts on which microscopic, decomposing animals sit. Nevertheless, they also colonize the soil layer or near the ground in extreme biotopes and ecosystems such as dunes , moors , heaths . The pedipalps feel ahead, which, like the long legs, serve as buttons. With a few exceptions, harvesters are nocturnal.
Very high densities of individuals can be observed in semi -natural deciduous forests or field trees in humid locations or in swamp forests at night in late summer after prolonged drought. The activity is very dependent on the weather.
Some species come together to form resting communities in sheltered places during the day. Close together and in contact with the tarsi, they also form hibernation societies, which, however, can dissolve immediately with the slightest disturbance. These wintering societies can contain up to 70,000 individuals. Nevertheless, harvestmen are considered to be solitary; most of them only meet at mating season.
The intensification of forestry and agriculture led to a rapid loss of habitats such as hedgerows, Knicks and swamp forests , but also to a quantitative and qualitative reduction in the litter layer in meadows and forests, and other elements of these habitats, such as dead wood . This makes intensive land use the main cause of the decline in some species of this group of animals.
With the harvestmen, the sperm are transferred directly. Male and female face each other with their front bodies and the male leads his genitals through the chelicerae into the genital area of the female. The genital opening of both sexes is shifted by the formation of a chitin plate , in the case of the phalangioida to directly under the oral cavity. In the genital chamber that is created there is an erectable and movable tube which the females use to lay eggs ( ovipositor ) and the males use as a penis for copulation.
The eggs , the female lays into small holes or gaps on the ground, in some South American representatives of Gonyleptidae one was brooding observed in the male nest building and this, as well as the eggs and the young of many females, with which it has paired up, guarded .
Systematics of the harvestmen
The exact systematic position of the harvestmen within the arachnids has not yet been clarified. Kury (2003) shows the current status.
Classically, they are used as a sister group of the mite-like ( hooded spiders and mites ), whereby this is based solely on the reason that in these groups the second pair of legs is slightly longer than the others. The previously good-looking argument of flagellated sperm is now obsolete because the original hooded spiders clearly have flagellated sperm.
An alternative idea classifies the harvestmen as a sister group of a taxon consisting of scorpions , pseudoscorpions and roller spiders . The main reason here is based on the attachment points of the leg muscles and the structure of the vestibule.
Internally, the harvestmen are classically divided into the three subordinates Cyphophthalmi , Palpatores and Laniatores . According to phylogenetic studies, however, the group of the Palpatores does not form a natural group, but only includes members of the lineage of the Cyphophthalmi, which is why both original taxa are combined to the Cyphopalpatores.
This group includes all types of harvestmen common in Central Europe. These are divided into the following families (species selection incomplete):
- Sironidae (2 species in Europe)
- Travuniidae (1)
- Cladonychiidae (= Erebomastidae) (2)
- Thread anchor - Nemastomatidae (17)
- Dicranolasmatidae (1)
- Brettkanker - Trogulidae (10)
- Snail anchor - Ischyropsalididae (7)
Schneider - Phalangiidae (35)
- Amilenus aurantiacus
- Dicranopalpus gasteinensis
- Lacinius dentiger
- Lacinius ephippiatus
- Lacinius horridus
- Lophopilio palpinalis
- Mitopus morio
- Odiellus spinosus
- Oligolophus hanseni
- Oligolophus tridens
- Opilio canestrinii
- Opilio parietinus
- Opilio saxitilis
- Paroligolophus agrestis
- Phalangium opilio
- Platybunus bucephalus
- Rilaena triangularis
- Sclerosomatidae (19)
The Laniatores are mainly found in the tropical rainforests of South America. They are characterized by their robber-legged pedipalps and button-like second walking legs. The males of these animals are heavily armored and have very large hip joints ( coxes ), whereas those of the last pair of legs are armed with thorns. Some species are also decorated with eye-catching sculpture and thorns.
So far, fossils of this order are mainly known from amber from various deposits, especially from the Eocene to the Oligocene Baltic amber. The identified species (at least ten) belong partly to recent genera (e.g. Opilio ). The small number of individuals in amber compared to other arthropods is primarily due to the animals' ability to shed individual legs if this enables them to free themselves from a dangerous situation (such as the sticky resin surface). In fact, in addition to the uncommon complete specimens, innumerable individual legs of harvestmen are found in amber, which as a rule cannot be identified. Except in amber, fossil remains of harvestmen have been found in carbonic formations. The remarkable large gap in tradition between the Carboniferous (> 300 million years) and the Eocene (approx. 50 million years) can be explained by the soft-bodied training of the harvestmen, which makes fossilization very difficult.
In the USA in particular, the urban legend persists that harvestmen have an extremely strong poison that is even deadly for humans, but which they cannot inject into their victims due to their tiny jaw claws. Harvesters actually only have relatively small jaw claws that are too weak to injure human skin. However, the claws have no venom ducts for injection, and neither does the harvestman have any venom glands to produce such venom.
Hannibal is the name of a harvester figure in the book Maya the Bee .
- Jochen Martens: Harvesters, Opiliones. The animal world of Germany, part 64. VEB G. Fischer, Jena 1978.
- Adriano B. Kury: Checklist of Valid Genera of Opiliones of the World. 2003.
- Jeffrey W. Shultz: Evolutionary morphology and phylogeny of Arachnida . In: Cladistics . tape 6 , no. 1 , 1990, p. 1-38 , doi : 10.1111 / j.1096-0031.1990.tb00523.x .
- Weitschat & Wichard: Baltic Amber. In: Biodiversity of fossils in amber from the major world deposits. Pp. 80-115, Ed .: David Penney, Manchester (UK) 2010, ISBN 978-0-9558636-4-6 .
- Weitschat & Wichard: Atlas of the plants and animals in the Baltic amber. Munich 1998, ISBN 3-931516-45-8 .
- Larsson: Baltic amber - a palaeobiological study. In: Entomonograph 1, Klampenborg (DK) 1978, ISBN 87-87491-16-8 .
- Müller: Textbook of Palaeozoology. Volume II Invertebrates, Part 2 Mollusca 2 - Arthropoda 1, Jena 1981.
- The Spider Myths Site: Daddy-Longlegs
- Jochen Martens: Harvesters, Opiliones. The animal world of Germany, part 64. VEB G. Fischer, Jena 1978.
- Heiko Bellmann : Cosmos Atlas Arachnids of Europe. 3. Edition. Kosmos, Stuttgart 2006, ISBN 978-3-440-10746-1 .
- Ralph Platen, Bodo von Broen u. a .:List of total species and red list of spiders, harvestmen and pseudoscorpions of the state of Brandenburg (Arachnida: Araneae, Opiliones, Pseudoscorpiones) of the state of Berlin.(PDF; 238 kB) In: Landesumweltamt Brandenburg (Hrsg.): Nature protection and landscape maintenance in Brandenburg. 8, No. 2, 1999 (supplement).
- Systematics of the arthropods
- Trembling spiders (Pholcidae), which are often confused with harvestmen.